1. Field of the Invention
This invention relates to a body structure of a motor vehicle and more particularly to an underbody sub-assembly and a body side frame sub-assembly and the securing of the assemblies together.
2. Description of the Relevant Art
Modern day motor vehicles typically have a unibody constructed of a series of panel members and U-shaped or channel shaped frame members of stamped sheet metal. The members are placed and clamped in a jig in order to position the members relative to each other for welding together to form a body structure.
It is known to assemble several sub-assemblies, including a pair of body side frame sub-assemblies and an underbody sub-assembly prior to placing the sub-assemblies in the jig and welding them together to form the body structure. Referring to FIG. 10, each of the body side frame sub-assemblies 120 has a box structure 122 extending longitudinally having a downward depending flange 124 that extends parallel to the centerline of the vehicle. The body side frame sub-assemblies are precisely spaced from each other in the jig. The underbody sub-assembly 126 is a generally planar floor pan member 128 which has a pair of outboard downward depending flanges 130. The underbody sub-assembly is raised upward into the jig between the two precisely spaced body side frame sub-assemblies and clamped so that the downward depending flanges can be welded together. The downward depending flanges on both the underbody and the body side frame sub-assemblies might require flexing in order to position and secure the underbody sub-assembly to the precisely spaced body side frame sub-assemblies. The flexing required to clamp the flanges together could be result of build variations which resulted in material thickness and dimension variations and cause in stress in the sub-assemblies.
When the body structure is removed from the jig after the sub-assemblies are welded together, it is possible that the body structure may flex to relieve the stress. The body structure must later be adjusted to compensate for the flex in order to ensure that the exterior panels and doors fit properly.
It would be desirable to have a vehicle body where the assemblies are positioned relative to each other for securing to each other so that any minor build variation in one of the assemblies does not compound during assembly of the assemblies, thereby the vehicle body is assembled without unnecessary stress on the body structure.